Question

Which of the exonucleases of NER binds to which end of the lesion?

(a) XPD on 3’ end and XPB on 5’ end

(b) XPF on 3’ end and XPA on 5’ end

(c) XPG on 3’ end and XPF on 5’ end

(d) XPD on 3’ end and XPA on 5’ end

I had been asked this question in semester exam.

Asked question is from Repair of DNA Damage: NER, Direct Reversal in section DNA Mutation, DNA Repair, Transposable Elements of Cytogenetics

Answer 1

Right choice is (c) XPG on 3’ end and XPF on 5’ end

To explain I would say: While XPD and XPB bind to the 3’ and 5’ end respectively, they are helicases and not exonucleases. On the other hand XPF along with ERCCI that binds to 5’ end and XPG are exonucleases.